Since they replaced the PCV valve hose I'd like to suggest that they either disconnected or pulled apart another hose connection or made poor connections with the new hose they installed and now there is a vacuum leak. A small vacuum leak will be worse when lightly pressing the gas pedal than if it were pressed down further.

I feel sorry for the people who don't drink. When they wake up in the morning, thats the best they're going to feel all day - former President Lyndon B. Johnson